Since there is a very strong connection with Rhino and Moi, it would also be very nice if Moi had a system that transfers layer data to and from Rhino... In general i think Rhino's sytem of layer management (speaking of Rhino 4) is very simple and effective. It's also nice because groupings are layer/sublayer independent, and you can assign group names, object names, etc... The only thing missing is hierarchies. If Moi used Rhino 4's system but added the (optional) function of hierarchies into the sublayers that would be pretty ideal for me. My idea is just a small button which drops down to show a list of hierarchy options :

**no hierarchy connection, after selected the button will display as " T "
**link to next level in the branch, after selected the button will display as " + "
**link to top level in the branch, after selected the button will display as " - "

jonah